SSH 経由でサーバーに接続できませんが、その理由がわかりません。
SSHD は実行中で、UFW でポートは開いています。ポートを変更してみましたが、問題は解決しません。別のマシンやネットワークも試しました。
サーバーを再起動すると、接続を確立できる場合もありますが、しばらくすると問題が再発します。
私のsshd_config:
# $OpenBSD: sshd_config,v 1.103 2018/04/09 20:41:22 tj Exp $
# This is the sshd server system-wide configuration file. See
# sshd_config(5) for more information.
# This sshd was compiled with PATH=/usr/bin:/bin:/usr/sbin:/sbin
# The strategy used for options in the default sshd_config shipped with
# OpenSSH is to specify options with their default value where
# possible, but leave them commented. Uncommented options override the
# default value.
Port 1402
#AddressFamily any
#ListenAddress 0.0.0.0
#ListenAddress ::
#HostKey /etc/ssh/ssh_host_rsa_key
#HostKey /etc/ssh/ssh_host_ecdsa_key
#HostKey /etc/ssh/ssh_host_ed25519_key
# Ciphers and keying
#RekeyLimit default none
# Logging
#SyslogFacility AUTH
LogLevel VERBOSE
# Authentication:
#LoginGraceTime 2m
#PermitRootLogin prohibit-password
StrictModes yes
#MaxAuthTries 6
#MaxSessions 10
#PubkeyAuthentication yes
# Expect .ssh/authorized_keys2 to be disregarded by default in future.
#AuthorizedKeysFile .ssh/authorized_keys .ssh/authorized_keys2
#AuthorizedPrincipalsFile none
#AuthorizedKeysCommand none
#AuthorizedKeysCommandUser nobody
# For this to work you will also need host keys in /etc/ssh/ssh_known_hosts
#HostbasedAuthentication no
# Change to yes if you don't trust ~/.ssh/known_hosts for
# HostbasedAuthentication
#IgnoreUserKnownHosts no
# Don't read the user's ~/.rhosts and ~/.shosts files
#IgnoreRhosts yes
# To disable tunneled clear text passwords, change to no here!
#PasswordAuthentication yes
PermitEmptyPasswords no
# Change to yes to enable challenge-response passwords (beware issues with
# some PAM modules and threads)
ChallengeResponseAuthentication yes
# Kerberos options
#KerberosAuthentication no
#KerberosOrLocalPasswd yes
#KerberosTicketCleanup yes
#KerberosGetAFSToken no
# GSSAPI options
#GSSAPIAuthentication no
#GSSAPICleanupCredentials yes
#GSSAPIStrictAcceptorCheck yes
#GSSAPIKeyExchange no
# Set this to 'yes' to enable PAM authentication, account processing,
# and session processing. If this is enabled, PAM authentication will
# be allowed through the ChallengeResponseAuthentication and
# PasswordAuthentication. Depending on your PAM configuration,
# PAM authentication via ChallengeResponseAuthentication may bypass
# the setting of "PermitRootLogin without-password".
# If you just want the PAM account and session checks to run without
# PAM authentication, then enable this but set PasswordAuthentication
# and ChallengeResponseAuthentication to 'no'.
UsePAM yes
#AllowAgentForwarding yes
AllowTcpForwarding no
#GatewayPorts no
X11Forwarding no
#X11DisplayOffset 10
#X11UseLocalhost yes
#PermitTTY yes
PrintMotd no
#PrintLastLog yes
#TCPKeepAlive yes
#PermitUserEnvironment no
#Compression delayed
KeepAlive yes
ClientAliveInterval 90000
ClientAliveCountMax 2
UseDNS no
#PidFile /var/run/sshd.pid
#MaxStartups 10:30:100
#PermitTunnel no
#ChrootDirectory none
#VersionAddendum none
# no default banner path
#Banner none
# Allow client to pass locale environment variables
AcceptEnv LANG LC_*
# override default of no subsystems
Subsystem sftp /usr/lib/openssh/sftp-server
# Example of overriding settings on a per-user basis
#Match User anoncvs
# X11Forwarding no
# AllowTcpForwarding no
# PermitTTY no
# ForceCommand cvs server
PermitRootLogin no
PasswordAuthentication yes
sshでタイムアウトエラーが発生します[メールアドレス]-p 1402
そして、nmap は次のように答えます。
user@linux:~$ nmap -p 1402 -Pn xx.xxx.xxx.xxx
Starting Nmap 7.70 ( https://nmap.org ) at 2021-09-07 22:06 CEST
Nmap scan report for xx.xxx.xxx.xxx
Host is up.
PORT STATE SERVICE
1402/tcp filtered prm-sm-np
Nmap done: 1 IP address (1 host up) scanned in 6.99 seconds
何かアイデアはありますか?
編集
UFW 設定
user@localhost:~$ sudo ufw status verbose
[sudo] password for user:
Status: active
Logging: on (low)
Default: deny (incoming), allow (outgoing), disabled (routed)
New profiles: skip
To Action From
-- ------ ----
1402/tcp LIMIT IN Anywhere
3000/tcp ALLOW IN Anywhere
9100/tcp ALLOW IN Anywhere
12798/tcp ALLOW IN Anywhere
6000/tcp ALLOW IN Anywhere
60000/tcp ALLOW IN Anywhere
1402/tcp (v6) LIMIT IN Anywhere (v6)
3000/tcp (v6) ALLOW IN Anywhere (v6)
9100/tcp (v6) ALLOW IN Anywhere (v6)
12798/tcp (v6) ALLOW IN Anywhere (v6)
6000/tcp (v6) ALLOW IN Anywhere (v6)
60000/tcp (v6) ALLOW IN Anywhere (v6)
答え1
KeepAlive yes
ClientAliveInterval 90000
ClientAliveCountMax 2
これらの 3 行は、90000*2 秒以内にクライアントから TCP パッケージがない場合、接続が自動的に切断されることを示しています。
これは SSH による保護メカニズムです。パラメータを変更するか、代わりに Bitvise ssh クライアントを使用すると、TCP ピンポン ハートビート パッケージがサーバーに自動的に送信されます。